The new cultivar is a product of a planned breeding program conducted by the inventor during 2009. May of 2009, the inventor, Friedrich Manfred Westphal, a citizen of Germany, made a crossing of the seed parent Clematis lanuginosa ‘Carnaby’, unpatented, with the pollen parent, Clematis patens ‘Rosa Konigskind’, unpatented Seeds originating from this crossing were planted out, and the new variety was selected during 2010. All work was conducted at a commercial nursery in Prisdorf, Germany.
The inventor first propagated ‘Passion Plum’ by vegetative cuttings at the commercial nursery in Prisdorf, Germany in April of 2010. Subsequent generations have shown that the unique features of this cultivar are stable and reproduced true to type.